The invention discloses a machine for examining a nuclear reactor fuel assembly having a flooring, support means for an assembly to be examined, which keep the latter in the vertical position, means for examining the assembly and means for displacing the examination means, said displacement means incorporating a vertically extending column and resting on the flooring. The column carries a bracket which is vertically displaceable along the column. The bracket supports a trolley or carriage which is transversely displaceable relative to the bracket.
A fuel assembly for a nuclear reactor, particularly a water-cooled reactor is constituted by a large number of sheath fuel and/or fertile rods or slugs kept in a parallel bundle by a rigid structure formed from two end pieces, respectively an upper end piece and a lower end piece, which are interconnected by metal bars. These assemblies are arranged in the core of the reactor between two plates, namely a lower plate and an upper plate.
It is necessary to inspect these fuel assemblies, particularly to detect any deformations of the rods and/or the retaining structure and also to detect risks of cracking. During reactor shutdown, certain assemblies which have operated under pressure and high temperature are discharged and transferred with the aid of appropriate handling means to an examination machine, which makes it possible to inspect the same.
In general terms, a fuel assembly examination machine has a support on which the assembly to be examined is vertically positioned and means for examining the assembly, which can be displaced relative to the latter, generally along three orthogonal axes.
For example, French patent No. 2,298,859 filed on 22.1.1975 for an "Apparatus and installation for the examination of fuel rods of a nuclear reactor" discloses a machine of this type. It has three movable trolleys or carriages, the first being vertically displaced on slides parallel to the assembly fuel rods, the second being horizontally displaced on slides carried by the first trolley or carriage and the third being displaced horizontally perpendicular to the second. The examination means, constituted by an endoscope carried by the third carriage can consequently be displaced in three perpendicular directions.
In addition, a machine for examining a nuclear reactor fuel assembly is known, which has a base B, a column C mounted at the end of the base and a platform D fixed at the end thereof opposite to that of the column. Platform D can rotate. Means 22 make it possible to rotate the same. Examination means can be moved vertically along column C. However, a disadvantage of these examination machines is that they do not permit an adequate moving back of the examination means.
Thus, in the case of the examination machine described in the aforementioned French patent No. 2,298,859, the possibilities of moving back the examination means are limited by the dimensions of the first trolley or carriage. These dimensions could certainly be increased, but this would have the disadvantage of simultaneously increasing the weight and overhang of the latter. In addition, the displacement means of the examination means do not constitute an easily dismantlable assembly, which can be replaced in case of need. The examination means according to the invention obviates these disadvantages. Therefore, the invention discloses a machine for examining a fuel assembly which permits greater displacements.
This problem is solved by the fact that the column is fixed to a trolley, which is displaceable on the flooring, which makes it possible to move the column towards or away from the assembly to be examined. This feature makes it possible to adapt the invention to various functions as a result of its displacement capacity. These can consist of examination with a camera, specific measurement with especially designed equipment, such as ultrasonic measuring devices, eddy current devices or laser means. It is also possible to adapt a machining device, e.g. for drilling or milling.
Moreover, the invention discloses an examination machine for the fuel assemblies of nuclear reactors having a flooring, means for supporting an assembly to be examined, which keep the assembly in the vertical position, means for examining the assembly, and means for displacing the latter, a support structure located at one end of the flooring and a chamber or container rotating about its vertical axis and receiving the assembly.
U.S. Pat. No. 3,621,580 discloses an examination means of this type. In this machine, the fuel assembly to be examined rests in the vertical position on a support which is rotatable by means of a manually operable hand wheel. The assembly is held in its upper part by a member, which can be fixed at an appropriate height to the column supporting the examination means. Such a machine makes it possible to rotate the assembly. However, it does not make it possible to immobilize it at characteristic positions which are accurately defined by gradually rotating the same. Moreover, the assembly is not accurately maintained in the position which it occupied when still in the reactor core.